The science behind personality fluctuations

After a recent parent-teacher meeting, a friend of mine called me, clearly anxious. Her son’s teacher described him as relaxed, sociable, and well-mannered, but at home, she often saw him withdrawn and irritable. She worried she might be dealing with a mini Dr. Jekyll and Mr. Hyde—like her son was leading a double life. “Should I be concerned?” she asked.

I reassured her, “Not at all. It’s not that he has two personalities; he’s just showing different sides of himself with different people.”

I went on to explain that it’s normal for us all to show different parts of ourselves in different settings. Maybe school feels structured and safe, but something at home might be bothering him. I asked her, “Think about it—don’t you act a little differently around your parents than you do with friends?” We all do. People are way too complex to fit into just one box.

Our personalities aren’t rigid; they adapt to the context we're in.

If you’ve ever taken a personality test, you might remember pausing on certain questions, thinking, “Well, it depends.” The Five Factor model—considered the gold standard for personality tests—asks you to rate yourself on traits like “is talkative,” “tends to be lazy,” or “can be moody.” And most people struggle to answer because, well, it really does depend on the situation.

And they’re right. Traditional personality theories suggest our traits are stable over time and across situations. People do show consistent patterns, but this doesn’t mean we act the same everywhere. Contemporary models of personality, like social-cognitive theories, argue that context matters.

To truly understand someone, we need to look at patterns across different situations. Who we are is a mix of our core traits and the environments we’re in. That’s why personality research in the past few decades has been focusing on how we express different parts of our personalities depending on where we are.

The writer Anaïs Nin had a perspective that challenged the idea of a fixed personality. In The Diary of Anaïs Nin, she wrote:

[…]My life is not possible to tell. I change every day, change my patterns, my concepts, my interpretations. I am a series of moods and sensations. I play a thousand roles. I weep when I find others play them for me. My real self is unknown. My work is merely an essence of this vast and deep adventure.

Maybe Nin’s view feels a bit radical—most of us aren’t rewriting ourselves every day. But it’s a helpful reminder: our personality isn’t set in stone.

We like to think there’s a steady, consistent “me” guiding our choices, and there is—sort of. Personality is definitely not a myth. But we also adapt. We tune into the moment and the people around us. Does that make us fake? Not at all. This isn’t about being unstable. It’s a sign of psychological flexibility. Think of it like jazz improvisation: the experienced musician doesn’t play the same tune in every room. They’re reading the crowd, matching the mood. Same musician, different vibe.

Writing about this reminds me of one of my favorite lines from The Selected Letters of Philip K. Dick:

A person’s authentic nature is a series of shifting, variegated planes that establish themselves as he relates to different people; it is created by and appears within the framework of his interpersonal relationships.

Philip Dick is right. Different situations bring out different sides of us. Take me, for example. On stage—whether I’m giving a lecture or speaking at a conference—I’m animated and confident, almost extroverted. But in my personal life, I’m more reserved, often preferring quiet and solitude. Does that mean I’m pretending when I’m on stage? Not at all. Speaking to an audience energises me, and it feels natural to act in a way that aligns with that energy. But at a crowded networking event, you’d probably find me quietly observing in the corner. We’re all a bit like this—different facets of ourselves showing up depending on where we are.

Research backs this up. In one study, people rated their personalities in different social situations. Around parents, they felt less emotionally stable, less open, and less agreeable. With friends, they felt more outgoing and open, while at work, they were  more conscientious. Another study showed that people felt more emotionally unstable with their romantic partners and at work. They also felt calmer with friends. In family or romantic settings, they felt less agreeable than they did at work.  

This makes sense. At work, we want to seem agreeable and cooperative because we worry about our performance, and we want to build good relationships. With close family or partners, we feel safe and might let down our guard. And with friends, we’re more likely to be open and warm, free from the “serious” role we play at work.

Certain people even bring out unique parts of us. Some friends make us feel more adventurous or outspoken, while others have us quietly sipping tea and sharing deep thoughts. It’s not “faking it”—it’s just responding to different dynamics. In one study, researchers found that people’s extraversion changed depending on how friendly the people around them were. As the people they interacted with became less friendly, their extraversion dropped at the same rate.  

I like to think of personality as shaped by genetics and pretty stable overall, but flexible enough to let us adapt. Seeing personality as rigid can lead us to judge ourselves and others too harshly. If you’re a generally conscientious person—hard-working, structured, organised—you might feel guilty for sleeping in on a Saturday instead of working out. You may think, “This isn’t like me!” and start calling yourself lazy. But is it really out of character to take a break? A rigid view of personality can lead to guilt, while flexibility allows us to relax and just live.

Or consider a calm, collected friend who one day breaks down, sharing something deeply personal. They’re not suddenly “not themselves”—they just feel safe enough to show you a vulnerable side.

Think of Simone Biles, one of the greatest gymnasts of all time, known for her confidence, strength, and mental toughness. But during the 2021 Olympics, she stepped back from several events, showing a different side—one of vulnerability. Which one is the “real” Biles? Both are. Personality helps define us, but it’s also adaptable, shaped by different experiences.

This raises a big question: when we act outside our usual personality, does it feel inauthentic?

This was explored in a series of studies, and it turns out, deviations from typical traits did not lead to feelings of inauthenticity. Introverts, for instance, didn’t feel like they were “faking it” when they behaved more extroverted. In fact, they often felt truer to themselves. Researchers concluded that flexibility in behaviour is typically genuine. Authenticity, it turns out, isn’t about sticking to a strict personality label; it’s about responding naturally to each moment.

So, what can we take away from this?

1 - Go easy on yourself for those personality shifts.

See your personality shifts as adapting, not inconsistency. Sometimes we feel like we’re “not being ourselves” when we act differently in different situations. But responding to each environment is a strength, not a flaw. Instead of judging yourself for being quieter at work or more relaxed with friends, appreciate that you’re adapting to the unique needs of each context.

2 - Resist snap judgments about new people.

First impressions can be misleading. That laid-back friend might seem all business at work, while the quiet coworker at the meeting might be the life of the party outside the office. Rather than assuming someone’s behaviour defines them, think about what might be influencing them.

3 - If you want to grow certain traits, pick people who bring them out.

Completely changing a trait is tough, but you can shape it. Because where you are and who you are with influence your behaviours in the moment, over time, these influences can accumulate, shaping the kind of person you become. Want to be more assertive? Hang around assertive people Want to become more hard-working and organised? Sit next to the coworker who’s conscientious.

4 - Choose your settings mindfully.

Since our personality traits shift based on our environment, adjusting your mood or behaviour can often be as simple as selecting the right setting. For instance, if you’re in a workplace where people are unfriendly, uncooperative, or lack compassion, it’s likely to impact both your mood and behaviour. Opting for a more collaborative and supportive environment can positively shape your behaviour and overall experience.

5 - Remember, authenticity isn’t about sticking to one version of yourself.

Just because a personality test says you score high on introversion doesn’t mean acting differently feels fake. People feel most authentic when acting naturally, not when they’re trying to fit a label. Embracing your flexibility can help you feel truer to yourself than any personality test result ever could.

At the end of the day, maybe the best version of “being yourself” is just staying open. Open to all the parts of you that show up in different moments, with different people, in different places. Personality isn’t a mold we have to fit into; it’s more like a collection we carry—a mix of strengths, quirks, and contradictions that make us who we are. So, rather than hunting for a single, stable identity, maybe it’s better to ask: What’s the most real part of me I can bring to this moment?

And that’s as close to “being yourself” as it gets.